They include four comets, and 22 Near Earth Objects (NEOS), of whcih three are large asteroids "hundreds of meters in diameter and black as coal".

Above: More than 100 asteroids were captured in this view from NASA's Wide-field Infrared Survey Explorer, or WISE, during its primary all-sky survey.

So far there is no indication that any of those asteroids will hit the Earth any time soon - but it is a reminder that there are still many, many things in nearby space that we either haven't seen, or haven't measured.

NeoWise gives Nasa the ability to measure the position and brightness of objects in the Solar System in a more precise and complete manner than previously.

Nasa said that of the 10,500 NEOs so far known about, only 10% have been measured. NeoWise will double that number to about 20%. Better, but probably not that reassuring in the long run.